Process for preparing elastomeric ethylene-hexafluoropropylene copolymer

ABSTRACT

According to the present invention, ethylene, HFP and when in demand, a monomer copolymerizable therewith can be emulsion polymerized at a low temperature of −20° C. to 40° C. at a high polymerization rate. Furthermore, the obtained elastomeric E-HFP copolymer has few branches and is excellent in processability.  
     Also, as mentioned before, the obtained vulcanizate has excellent heat resistance, oil resistance, amine resistance and chemical resistance and can be used for various parts in the automobile, aircraft and semiconductor industries. Utilizing this heat resistance, oil resistance and amine resistance, the vulcanized composition is particularly suitable for oil seal or oil seal parts such as a hose for the engine oil, ATF oil, gear oil and CVT oil of an automobile.

TECHNICAL FIELD

[0001] The present invention relates to a process for preparing anelastomeric E-HFP copolymer, with ethylene (E) and hexafluoropropylene(HFP) as fundamental monomers, efficiently at a low temperature with astable composition.

[0002] The vulcanizate obtained by vulcanizing a vulcanizablecomposition obtained by using this elastomeric E-HFP copolymer isexcellent in amine resistance and is suitable as material for oil sealfor automobile oil, especially engine oil, mission oil and differentialoil.

BACKGROUND ART

[0003] The elastomeric copolymer of ethylene (E) and hexafluoropropylene(HFP) is excellent in heat resistance, oil resistance and chemicalresistance (particularly alkali resistance), just as other fluorineresin and elastomers are.

[0004] Because the copolymerizability of ethylene andhexafluoropropylene is extremely low and the copolymerization reactiondoes not proceed in moderate polymerization conditions, copolymerizationhas been conducted under severe polymerization conditions of highpressure or using radiation in the past.

[0005] For example, in J. Polym. Sci. A, 12, page 627 (1974),copolymerization is conducted in a high pressure of 4.9 MPaG (50kgf/cm²G) by irradiating with radiation at ambient temperature. However,using radiation requires special facilities and is not suitable in termsof safety.

[0006] The method of copolymerizing ethylene and HFP at a hightemperature and high pressure (650 kg/cm² to 2,000 kg/cm², 115 to 200°C.) batchwise or continuously is disclosed in the Journal of theChemical Society of Japan, 1980, (1), p 112 to 120. However, though thevulcanization properties of the obtained copolymer are excellent, thepolymerization method is not emulsion polymerization. In addition, asmentioned before, because the reaction conditions are extremely harsh,there is the problem of an increase in the building costs of theproduction facilities.

[0007] U.S. Pat. No. 4,039,595 describes conducting copolymerization ata low temperature of 30° C. at 3.76 MPaG (545 psiG) using apolymerization initiator such as diisopropyl peroxydicarbonate. However,the polymerization method is suspension polymerization and the obtainedcopolymer is a low molecular weight substance without elastomericproperties.

[0008] WO 94/24175 pamphlet describes copolymerizing ethylene, HFP andtetrafluoroethylene (TFE) at 50° C. under high pressure of 3.43 MPaG (35kgf/cm²G) using ammonium persulfate as a polymerization initiator.However, the polymerization rate is low and the obtained copolymer hasmany branches and is inferior in processability.

[0009] Furthermore, as a method for preparing a fluorine-containingelastomer by copolymerizing at a low temperature, JP-A-56-163105describes redox polymerization using water soluble persulfate and areducing agent comprising hydroxymethane sulfinate andethylenediaminetetraacetic acid or a salt thereof. However, there are nodescriptions mentioning E-HFP copolymers or the increase invulcanization properties by lowering the polymerization temperature.

[0010] The present invention aims to provide a process for preparing anelastomeric E-HFP copolymer with few branches, large molecular weightand excellent vulcanization properties.

DISCLOSURE OF INVENTION

[0011] The present invention relates to a process for preparing anelastomeric ethylene-hexafluoropropylene copolymer which comprisesemulsion-polymerizing ethylene (E), hexafluoropropylene (HFP), and whenin demand, a monomer copolymerizable therewith in an aqueous medium at−20° C. to 40° C. using a radical polymerization initiator.

[0012] The radical polymerization initiator may be used independently,but it is preferable that copolymerization is conducted in the presenceof a redox-type initiator by using a radical polymerization initiatorand a reducing agent comprising metal ion, hydroxymethane sulfinate andethylenediaminetetraacetic or a salt thereof.

[0013] As the radical polymerization initiator, organic peroxide orpersulfate may be used suitably.

[0014] As the organic peroxide, peroxyesters such as t-butylperoxypivalate are preferable.

[0015] Furthermore, emulsion polymerization can be conducted under arelatively low polymerization pressure of 0.49 to 10 MPaG.

BEST MODE FOR CARRYING OUT THE INVENTION

[0016] In the present invention, the copolymerization ratio (mole ratio)of the monomers, E/HFP, is 90/10 to 50/50, more preferably 70/30 to50/50. The monomers may be copolymerized so that the amount of the othermonomers copolymerizable therewith is 0 to 15% by mole, more preferably0 to 10% by mole.

[0017] Examples of the monomers copolymerizable with ethylene and HFPare tetrafluoroethylene (TFE), vinylidene fluoride (VdF),chlorotrifluoroethylene (CTFE), trifluoroethylene, pentafluoropropyleneand perfluoro(alkyl vinyl ether) (PAVE), or at least two members of themonomers. TFE and CTFE are particularly preferable from the viewpointthat productivity can be improved. However, it is necessary for theobtained copolymer to have elastomeric properties.

[0018] The radical polymerization initiator used in the presentinvention is important in increasing the polymerization reaction rate ata low temperature. As the radical polymerization initiator, organicperoxide, persulfate or a redox type initiator which is a combination ofthese with a reducing agent is suitable.

[0019] Examples of organic peroxides include peroxyesters such as1,1,3,3-tetramethylbutyl peroxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexyl peroxyneodecanoate, t-butylperoxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate,1,1,3,3-tetramethylbutyl peroxy2-ethylhexanoate,2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane,1-cyclohexyl-1-methylethyl peroxy2-ethylhexanoate, t-hexylperoxy2-ethylhexanoate, t-butyl peroxy2-ethylhexanoate, t-butylperoxyisobutylate, t-hexyl peroxyisopropyl monocarbonate, t-butylperoxy3,5,5-trimethylhexanoate, t-butyl peroxylaurate, t-butylperoxyisopropylmonocarbonate, t-butyl peroxy2-ethylhexylmonocarbonate,t-butyl peroxyacetate, t-butyl peroxybenzoate, and cumylperoxyneodecanoate; dialkylperoxides such as2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, di-t-butyl peroxide;diacylperoxides such as isobutyryl peroxide, 3,5,5-trimethylhexanoylperoxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide andsuccinic acid peroxide; peroxy dicarbonates such as dinormalpropylperoxydicarbonate, diisopropyl peroxydicarbonate,bis(4-t-butylcyclohexyl)peroxy dicarbonate, di-2-ethoxyethylperoxydicarbonate, di-2-ethylhexyl peroxydicarbonate anddi-2-methoxybutyl peroxydicarbonate; hydroperoxide such as p-methanehydroperoxide, diisopropylbenzene hydroperoxide,1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexylhydroperoxide and t-butyl hydroperoxide;

[0020] and the like.

[0021] Of these, peroxyesters, especially t-butyl peroxypivalate, arepreferable from the viewpoint that polymerization rate is high and themolecular weight of the obtained copolymer is high.

[0022] Examples of the persulfate are ammonium salt such as ammoniumpersulfate and alkali metal salt such as sodium persulfate, potassiumpersulfate and the like. Of these, from the viewpoint of high watersolubility, ammonium persulfate is preferable.

[0023] Examples of the reducing agents, which form a redox typeinitiator when used in combination with these, are metal ion,hydroxymethane sulfinate, ethylenediaminetetraacetic acid (EDTA), a saltthereof, water-soluble thiosulfate, sulfite and the like.

[0024] Examples of the metal ion are ions of iron, copper, silver,cerium, cobalt and nickel. These are supplied in the form of sulfite,chloride, ammonium sulfate, nitrate and the like.

[0025] Ethylenediaminetetraacetic acid (EDTA) may be used in an isolatedform but more preferably is used in the form of disodium salt.

[0026] An example of an especially preferable redox type initiator is acombination using a peroxyester or persulfate as the radicalpolymerization initiator and iron ion (iron sulfate), EDTA (or a saltthereof) and hydroxymethane sulfinate as the reducing agent. Of these,the combination using t-butylperoxypivalate (radical polymerizationinitiator), iron ion (iron sulfate), EDTA (or a salt thereof) andhydroxymethane sulfinate is most preferable form the viewpoint that thepolymerization reaction rate is high at a low temperature and themolecular weight can be easily adjusted.

[0027] The proportion of the radical polymerization initiator and thereducing agent is preferably 1 to 100 mmol/l (concentration in aqueousmedium within the emulsion polymerization system; same below),particularly 5 to 50 mmol/l of the radical polymerization initiator,0.005 to 5 mmol/l, particularly 0.01 to 1 mmol/l of metal ion (metalsalt, particularly iron salt), 0.005 to 5 mmol/l, particularly 0.01 to 1mmol/l of EDTA and 0.5 to 100 mmol/l, particularly 5 to 50 mmol/l ofhydroxymethane sulfinate.

[0028] By changing the charging amount and ratio of metal (iron) ion andEDTA, the polymerization reaction speed and the molecular weight of theobtained copolymer can be controlled.

[0029] The amount of radical polymerization initiator is 0.001 to 5% byweight, preferably 0.01 to 5% by weight based on the total amount ofmonomers. The amount of the redox type initiator is determined inrelation to the amount of the radical polymerization initiator withinthe above range. When the amount of the radical polymerization initiatoris large, the molecular weight becomes small, and the obtained copolymeris not elastomeric.

[0030] A characteristic and the biggest effect of the present inventionlies in the improvement of vulcanization properties of the elastomergenerated by radical emulsion polymerization at a low temperature of−20° C. to 40° C., more preferably 5° C. to 35° C. Polymerization can beconducted at a polymerization temperature which exceeds 40° C., but thisrange is not included in the present invention as the vulcanizationproperties decrease. In addition, too low a temperature is notpreferable because the polymerization rate becomes low.

[0031] The emulsion polymerization of the present invention can beconducted under a relatively low polymerization pressure. Usually apressure of at most 10 MPa, preferably at least 0.49 MPa, morepreferably approximartely 0.49 to 3 MPa is employed. Emulsionpolymerization progresses even when the polymerization pressure is high,but this is a disadvantage because production facility costs increase.

[0032] The emulsion polymerization of the present invention is conductedby emulsifying the aforesaid monomer and radical polymerizationinitiator (or redox type initiator) within an aqueous medium.Emulsification of a monomer is usually conducted using an emulsifier.The emulsifier used for emulsion polymerization for obtaining E-HFPcopolymer can be employed. Examples of the emulsifier are fluorine typeemulsifiers such as perfluoro ammonium octanate, perfluoro ammoniumnonate and F(CF(CF₃)CF₂O)_(n)CF(CF₃)COONH₄ (n=1 to 4). Of these, aflourine type emulsifier such as perfluoro ammonium octanate ispreferable from the viewpoint that polymerization rate is high. Theamount used is 0.0001 to 15% by weight, more preferably 0.1 to 30% byweight based on the aqueous medium.

[0033] Other additives usually used in emulsion polymerization may beused according to need. For example, the polymerization system ispreferably neutral or slightly alkali with a pH of approximately 7 to 10in view of increasing the polymerization reaction rate. In order toadjust the pH, pH control agents such as sodium hydroxide, potassiumhydroxide, ammonium hydroxide and sodium hydrogen phosphate may beadded. Furthermore, water-soluble organic solvents such as methanol,t-butanol and methyl acetate may be used in order to advance thepolymerization reaction rate.

[0034] Though the polymerization time differs according to the type ofmonomer used, the type and amount of the radical polymerizationinitiator used, the desired molecular weight of the copolymer, thecomposition of the copolymer and the like, a range of 1 to 100 hours isappropriate.

[0035] The E-HFP copolymer obtained in this way has elastomericproperties and few branches, and is therefore excellent inprocessability.

[0036] A vulcanizate obtained by vulcanizing this elastomeric E-HFPcopolymer using a vulcanizer is excellent in vulcanization properties,especially strength at break, elongation at break and heat resistance.

[0037] The methods of peroxide vulcanization and radiation vulcanizationmay be employed for vulcanizing the elastomer obtained by the presentinvention.

[0038] As the peroxide used as vulcanizing agent in peroxidevulcanization, organic peroxide which easily generates peroxy radical byheat or in the presence of an oxidation reducing agent is preferablyused. Examples thereof include1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide,t-butylcumyl peroxide, dicumyl peroxide,2,5-dimethyl-2,5-bis(t-butylperoxy)hexane,α,α-bis(t-butylperoxy)-p-diisopropyl benzene,2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3, benzoyl peroxide, t-butylperoxybenzene, t-butyl peroxybenzoate,2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butyl peroxymaleic acid,t-butyl peroxyisopropylcarbonate,1,1-bis(t-butylperoxy)2-methylcyclohexane,1,1-bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)3,3,5-triethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane,1,1-bis(t-butylperoxy)cyclododecane, t-hexyl peroxybenzoate, t-butylperoxyacetate, 2-2-bis(t-butylperoxy)butane,n-butyl-4,4-bis(t-butylperoxy)pentanoic acid, di-t-butylperoxyisophthalate, 2,5-diethyl-2,5-di(benzoylperoxy)hexane and thelike. Of these, dialkyl type and peroxy ester type, in particulart-butyl peroxybenzoate and dicumyl peroxide are preferable.

[0039] The amount of the vulcanizing agent can be accordingly determinedwith consideration to the amount of active —O—O— bonds within theorganic peroxide and decomposition temperature, and is generally 0.5 to10 parts, preferably 1.0 to 5 parts based on 100 parts of the copolymer.

[0040] In peroxide vulcanization, hardening (vulcanization) advancessignificantly by using an auxiliary vulcanizing agent. Examples of theauxiliary vulcanizing agent are those which have been usedconventionally such as triallyl cyanurate, triallyl isocyanurate,triallyl formal, triallyl trimellitate, N,N′-m-phenylene bismaleimide,dipropargyl terephthalate, diallyl phthalate, tetraallylterephthalateamide, triallyl phosphate and the like. Of these, triallyl isocyanurateis preferable. The amount used is generally 0.2 to 10 parts, preferably0.5 to 5 parts based on 100 parts of the copolymer.

[0041] Peroxide vulcanization may be conducted in the conventionalmanner. For example, there is the method of putting, into a die, thecopolymer obtained by the present invention, a vulcanizing agent andwhen necessary, an auxiliary vulcanizing agent and any other additivewhich can be compounded accordingly after roll mixing and raising thepressure to carry out primary vulcanization, and then secondaryvulcanization. Usually, the conditions adopted for primary vulcanizationare within the ranges of 100° C. to 200° C. in temperature, 5 to 60minutes in time and 2 to 10 MPa in pressure. The conditions adopted forsecondary vulcanization are within the ranges of 150° C. to 300° C. intemperature and 30 minutes to 30 hours in time.

[0042] To the composition comprising the copolymer obtained by thepresent invention, a filler, a processing aid or an antioxidant may beadded according to need.

[0043] Examples of the filler are metal oxide such as magnesium oxide,calcium oxide, zinc oxide, lead oxide, titanium oxide, iron oxide,silver oxide, chromium oxide, bismuth oxide, silicon oxide, aluminumoxide and copper oxide, metal hydroxide such as magnesium hydroxide,aluminum hydroxide and calcium hydroxide, carbonate such as magnesiumcarbonate, aluminum carbonate, calcium carbonate and barium carbonate,metal sulfide such as molybdenum disulfide, iron sulfide and coppersulfide, sulfate such as calcium sulfate, aluminum sulfate and bariumsulfate and silicate such as magnesium silicate, calcium silicate,sodium silicate and aluminum silicate. Other examples are hydrotalcite,lithopone (a mixture of zinc sulfide and barium sulfate), graphite,carbon black, lampblack, carbon fluoride, calcium fluoride, coke,fluorine resin powder or fiber and carbon fiber.

[0044] Chromium oxide, silicon oxide and iron oxide powder which areinorganic powder with a Mohs hardness of at least 6, which are describedin JP-A-8-27343 and JP-A-8-151565; polytetrafluoroethylene powderpierced with carbon described in JP-A-7-188500; a fiber prepared with amaterial having a fluorine resin to which a filler is added as the maincomponent which is described in JP-A-56-151739; a fiber of a materialhaving carbon fiber and fluorine resin as the main component; andcalcium metasilicate or graphite which is described in JP-B-5-64177 arepreferable from the viewpoint of particularly contributing to theimprovement of abrasion resistance, metal adhesion and lubricatingproperties. Furthermore, carbon black and silicon oxide are preferablefrom the viewpoint of significant improvement in mechanical strength andpermanent compression strain.

[0045] Examples of the processing aid are higher fatty acids such asstearic acid, oleic acid, palmitic acid and lauric acid, higher fattyacid salts such as sodium stearate and zinc stearate, higher fatty acidamides such as stearic acid amide and oleic acid amide, higher fattyacid esters such as ethyl stearate, butyl stearate, ethyl oleate andbutyl oleate, higher fatty acid amines such as stearic acid amine,polyols such as ethylene glycol, glycerine and diethylene glycol,aliphatic hydrocarbons such as vaseline and paraffin and others such aspetroleum wax, silicone oil, low molecular weight polyethylene and lowmolecular weight polypropylene.

[0046] Examples of antioxidants are4,4-bis(α,α-dimethylbenzyl)diphenylamine, phenyl-1-naphthylamine,alkylated diphenylamine, octylated diphenylamine,p-p(toluenesulfonylamide)diphenylamine,N,N′-di-2-naphthyl-p-phenylenediamine, N,N′-diphenyl-p-phenylenediamine,N-phenyl-N′-isopropyl-p-phenylenediamine,N-phenyl-N′-(1,3-dimethylbutyl)-p-phenylenediamine),N-phenyl-N′-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine,2,2,4-trimethyl-1,2-dihydroquinoline polymer andtris(nonylpheny)phosphite.

[0047] When radiation vulcanization is employed, an auxiliaryvulcanizing agent, filler, processing aid and antioxidant may be addedto vulcanize as in peroxide vulcanization.

[0048] The vulcanizable composition in which the elastomer obtained bythe process of the present invention is used may be molded into moldedarticles such as a sheet, pipe, rod, tube, angle, channel, cloth productand coated board by continuous molding such as extrusion, transfer,calender, roll coat, brushing and impregnation in addition to the usualmolding using a die. The composition may also be molded into profilesand molded articles of a special shape such as spongy rubber, by otherknown molding methods. Also, the composition may be primarily processedinto film or tape and then further molded by secondary processing suchas laminating, attaching, and wrapping. The composition molded in thismanner is vulcanized by the aforementioned vulcanizing measures. Inaddition, a vulcanization coating can be formed by vulcanizing afterapplying the composition to the surface of the base material in thestate of a solution by coating, impregnating or spraying; byvulcanization adhesion by laminating the vulcanizable composition in astate of film or sheet; or by adhesion laminating the vulcanized film orsheet to the surface of the base material and thus various vulcanizedrubber products can be provided.

[0049] The vulcanizate obtained in this way has excellent heatresistance, oil resistance, amine resistance and chemical resistance andcan be used for various parts in the automobile, aviation,semiconductor, food and chemical industries. Utilizing the heatresistance, oil resistance and amine resistance, the composition issuitable for oil seal or oil seal parts such as a hose for the engineoil of an automobile. Other favorable molded articles are listed below.

[0050] Applications of Molded Articles:

[0051] Packing, O-ring, hose, other sealing materials, diaphragm valveand wire covering material for amine resistance, oil resistance,chemical resistance, steam resistance and weather resistance intransportation means such as automobile, ship and airplane; similarpacking, O-ring, sealing material, diaphragm, valve, hose, roll and tubein chemical plant; similar packing, O-ring, hose, sealing material,belt, diaphragm, valve, roll and tube in foods plant and foodsprocessing machine (including domestic appliances); similar packing,O-ring, hose, sealing material, diaphragm, valve and tube in nuclearplant; similar packing, O-ring, hose, sealing material, diaphragm,valve, roll, tube, mandrel, wire covering material, flexible joint,belt, rubber plate and weather strip in general industrial parts; rollblade for PPC copying machine, etc.

[0052] More concretely there are the following applications.

[0053] (i) Automotive Applications

[0054] The elastomer obtained by the present invention exhibits superiorheat resistance and resistance against amine type additive (morespecifically succinate imides and metal dialkyl dicarbamates) which aremainly added to automobile oil. In addition, because the volume changeis small in relation to the oil, the elastomer is suitable as variousparts and molded articles for automobile oil, such as automatictransmission fluid (ATF), engine oil and differential gear oil. Morespecifically, the elastomer is suitable as material for an elastomermolded article which may possibly come into contact with oil such assealing material or hose material for engine oil of gasoline and dieselpowered vehicles, sealing material or hose material for varioustransmission oil; sealing material or hose material for various gear oiland coating material for sensor lines to detect oil environment.

[0055] More Specifically,

[0056] (1) For Sealing

[0057] Crank shaft seal

[0058] O-ring and gasket for engine cylinder sleeve

[0059] O-ring and gasket for wet cylinder sleeve

[0060] Power piston packing

[0061] Cylinder liner seal

[0062] Valve stem seal

[0063] Front pump seal for automatic transmission

[0064] Rear axle pinion seal

[0065] Gasket for universal joint

[0066] Pinion seal for speed meter

[0067] Piston cup for foot brake

[0068] O-ring and oil seal for torque transmission

[0069] Seal for after-burner for exhaust gas

[0070] Bearing seal

[0071] Differential seal (drive pinion seal, side seal)

[0072] Differential gasket and O-ring

[0073] Oil seal, gasket, O-ring and packing for manual transmission

[0074] Oil seal, gasket, O-ring and packing for automatic transmission

[0075] Oil seal, gasket, O-ring and packing for gearless transmission(belt type or toroidal type)

[0076] Wheel bearing seal

[0077] Seal, gasket and O-ring for radiator

[0078] Seal, gasket and O-ring for oil cooler

[0079] Seal, gasket and O-ring for power steering

[0080] (2) For Hose

[0081] Oil hose for manual transmission

[0082] ATF hose for automatic transmission

[0083] CVTF hose for gearless transmission (belt type or toroidal type)

[0084] EGR tube

[0085] Twin-carburetor tube

[0086] Hose for radiator

[0087] Hose for oil cooler

[0088] Hose for power steering

[0089] (3) For Diaphragm

[0090] Diaphragm for sensor of carburetor (4) For Electrical Components

[0091] Wire covering material

[0092] Insulating material

[0093] Sheathe

[0094] Cooler hose

[0095] Tube

[0096] Ring

[0097] Packing (5) Other Applications

[0098] Vibration proof rubber (engine mount, exhaust system, etc.)

[0099] Hose for after burner

[0100] (ii) Applications in Chemical Industries

[0101] (1) For Sealing

[0102] Seals for pump, flow meter and pipe for chemicals

[0103] Seal for heat exchanger

[0104] Packing of glass cooler for sulfuric acid manufacturing equipment

[0105] Seals for sprinkler and transfer pump for agricultural chemicals

[0106] Seal for gas pipe

[0107] Seal for plating solution

[0108] Packing for high temperature vacuum dryer

[0109] Roll seal of belt for paper making

[0110] Seal for fuel battery

[0111] Joint seal for air duct

[0112] (2) For Roll

[0113] Roll having trichlene resistance (for dyeing of fiber)

[0114] (3) Other Applications

[0115] Acid resistant hose (for concentrated sulfuric acid)

[0116] Packing for joint of tubes for gas chromatograph and pH meter

[0117] Chlorine gas transfer hose

[0118] Rainwater drain hoses for benzene and toluene reservoir tanks

[0119] Seal, tube, diaphragm and valve parts for analyzer and physicaland chemical appliances

[0120] Steam hose

[0121] (iii) Applications for Industrial Machinery

[0122] (1) For Sealing

[0123] Seals for hydraulic and lubricating machine

[0124] Bearing seal

[0125] Seal for dry copying machine

[0126] Seals for window, etc. of dry cleaner

[0127] Seal for equipment for concentrating uranium hexafluoride

[0128] Seal (vacuum) valve for cyclotron

[0129] Seal for automatic packaging machine

[0130] (2) Other Applications

[0131] Rolls, scraper, tube and valve parts for printing equipment

[0132] Rolls, scraper, tube and valve parts for coating equipment

[0133] Ink tube, roll and belt for printer

[0134] Belt and rolls for dry copying machine

[0135] Diaphragms for pumps for analyzing sulfurous acid gas andchlorine gas in the air (environmental pollution-related meters)

[0136] Rolls and belt for printer

[0137] Squeeze rolls for pickling

[0138] Pipe, hose and flexible joint for dry-cleaning machine

[0139] (iv) Airplane Applications

[0140] Valve stem seal for jet engine

[0141] Fuel feeding hose, gasket and O-ring

[0142] Rotating shaft seal

[0143] Gasket for hydraulic equipment

[0144] Seal for fire wall

[0145] (v) Ship Applications

[0146] Stern seal for screw propeller shaft

[0147] Suction and exhaust valve stem seals for diesel engine

[0148] Valve seal for butterfly valve

[0149] Stem seal for butterfly valve

[0150] (vi) Food and Medicine Applications

[0151] Seal for plate heat exchanger

[0152] Solenoid valve seal for vending machine

[0153] Plugs for chemicals

[0154] Rubber material for food processing machine (for example sealingmaterial such as a gasket, diaphragm and O-ring for an heat exchanger,pipe, hose, sanitary packing, valve packing and filler packing used as ajoint between the mouth of the bottle and the filler when filling)

[0155] Packing, gasket, tube, diaphragm, hose and joint sleeve forfilling device, sterilizing device and brewing device of alcoholic andcarbonated beverage products, water heater and various automatic foodvending machines

[0156] (vii) Electrical Applications

[0157] Insulation oil cap for a train of the Shinkansen line

[0158] Venting seal for liquid ring transmission

[0159] Jacket for oil well cable

[0160] Electric insulating material (for example material used forinsulating spacer for various electric appliances and insulating tapeand heat contracting tube which is used for the joint and terminal partof cables)

[0161] Material for electronic and electric devices used in a hightemperature atmosphere (for example lead wire material for motor, wirematerial for high heat oven)

[0162] Further the molded article of the present invention can be usedfor O-ring, sealing material, hose, tube, diaphragm, roll, lining andcoating in equipment for producing semiconductor, liquid crystal panel,plasma display panel, plasma address liquid crystal panel, fieldemission display panel, substrate for solar battery, etc., for example,CVD equipment, etching equipment, oxidation/diffusion equipment,sputtering equipment, ashing equipment, ion implantation equipment,exhausting equipment, and the like which require plasma resistance;O-ring, sealing material, hose, tube, diaphragm and roll in wet etcher,cleaning equipment, pipes for chemicals, gas pipes, and the like whichrequire chemical resistance; and further O-ring, sealing material, hose,tube, diaphragm and roll to be used on parts of the mentioned equipmentwhich are required to be free from dust and metal.

[0163] Examples of other applications where chemical resistance isrequired are O-ring, sealing material, hose, tube, diaphragm of pump forresist developing solution, releasing solution and wafer cleaningsolution and wafer transferring rolls in production equipment forsemiconductor, liquid crystal panel, plasma display panel, etc.

[0164] Furthermore, there are other examples of using by forming avulcanization covering as mentioned before. More specifically, examplesare listed below.

[0165] Non-adhesive oil resistant roll for copying machine

[0166] Weather strip for weather resistance and freeze prevention

[0167] Rubber plug for fluid infusion

[0168] Vial rubber plug

[0169] Mold-releasing agent

[0170] Non-adhesive carrier belt

[0171] Adhesion preventing covering for the pre gasket of the automobileengine mount

[0172] Coating of synthetic fiber

[0173] Bolt member or joint having thin layer of coating of packing

[0174] Hereinafter, the present invention is explained in detail bymeans of examples, but is not limited thereto.

EXAMPLE 1

[0175] A 100 ml stainless steel autoclave was charged with 45 ml of ionexchanged water, 42.5 g of ammonium perfluorooctanate, 0.04 g of sodiumhydroxide, 0.4 g of hydrogen phosphate disodium salt 12 hydrate, 1.84 gof t-butyl alcohol and 0.13 g of Perbutyl PV (containing 70% by weightof t-butyl peroxy pivalate, available from NOF Corporation). Aftersufficiently replacing with nitrogen, the autoclave was charged with16.7 g of hexafluoropropylene (HFP) and then 2.02 g of ethylene in avacuum state. The autoclave was placed into a constant temperature waterbath shaker of 15° C. and was shaken until the pressure became constant(1.6 MPaG). When the pressure became constant, the autoclave was chargedwith an aqueous solution containing 0.0031 g of iron (II) sulfate 7hydrate, 0.0041 g of disodium ethylene diamine tetraacetate 2 hydrateand 0.1 g of sodium hydroxymethane sulfinate 2 hydrate by a plunger pumpto start the reaction. The reaction was conducted at 15° C. for 15hours.

[0176] After the reaction was finished, the remaining monomers werereleased into the air and the obtained emulsified dispersion body wascoagulated with hydrochloric acid, then washed with ion exchanged waterand dried at 120° C. until a constant weight was reached to obtain 9.9 gof the elastomeric polymer product. The average polymerization rate was13.2 g/hr/liter-water.

[0177] The composition of copolymer, number average molecular weight andweight average molecular weight of the product obtained by thepolymerization were measured by the analyzing method of ¹H-NMR and GPC.The product was a copolymer of 56.7% by mole of ethylene and 43.3% bymole of HFP, the number average molecular weight was 4.63×10⁴ (on apolystyrene basis), and the weight average molecular weight was1.14×10⁵.

EXAMPLES 2 TO 11

[0178] E-HFP copolymer was obtained by emulsion polymerizing ethyleneand HFP in the same manner as in Example 1 except that the radicalpolymerization initiators indicated in Table 1 in the amounts indicatedin Table 1 were used instead of Perbutyl PV (containing 70% by weight oft-butyl peroxypivalate, available from NOF Corporation).

[0179] The amount of the copolymer obtained, the average polymerizationrate, the composition of copolymer, the number average molecular weightand the weight average molecular weight in these Examples are indicatedin Table 1.

[0180] The radical polymerization initiators used are as follows.

[0181] Perbutyl PV: containing 70% by weight of t-butyl peroxypivalate,available from NOF Corporation.

[0182] Perbutyl L: containing 90% by weight of t-butyl peroxylaurate,available from NOF Corporation.

[0183] Perbutyl Z: containing 98% by weight of t-butyl peroxybenzoate,available from NOF Corporation.

[0184] Perbutyl A: containing 50% by weight of t-butyl peroxyacetate,available from NOF Corporation.

[0185] Perbutyl ND: containing 70% by weight of t-butylperoxyneodecanoate, available from NOF Corporation.

[0186] Percumyl ND: containing 70% by weight of cumylperoxyneodecanoate, available from NOF Corporation.

[0187] Perhexyl ND: containing 70% by weight of t-hexylperoxyneodecanoate, available from NOF Corporation.

[0188] Perocta ND: containing 70% by weight of 1,1,3,3-tetramethylbutylperoxyneodecanoate, available from NOF Corporation.

[0189] Perbutyl IB: containing 74% by weight of t-butylperoxyisobutylate, available from NOF Corporation.

[0190] Perloyl IB: containing 25% by weight of isobutyrylperoxide,available from NOF Corporation. TABLE 1 Radical Average molecular weightpolymerization initiator Average Amount of (×10⁴) Composition Amountpolymerization rate copolymer Number Weight of copolymer Type charged(g) (g/hr/liter-water) obtained (g) average average (E/HFP, % by mole)Ex. 1 Perbutyl PV 0.13 13.2 9.9 4.63 11.4 56.7/43.3 Ex. 2 Perbutyl L0.16 10.2 7.6 3.98 8.49 58.0/42.0 Ex. 3 Perbutyl Z 0.10 6.2 4.6 3.567.28 58.8/41.2 Ex. 4 Perbutyl A 0.14 6.9 5.1 3.58 7.06 59.1/40.9 Ex. 5Perbutyl ND 0.18 10.6 7.9 4.74 10.1 58.5/41.5 Ex. 6 Percumyl ND 0.23 9.47.0 3.80 7.69 58.4/41.6 Ex. 7 Perhexyl ND 0.20 11.0 8.3 4.06 8.4957.8/42.2 Ex. 8 Perocta ND 0.23 9.8 7.3 4.40 9.44 58.1/41.9 Ex. 9Perbutyl IB 0.11 8.7 6.5 3.54 6.98 58.3/41.7 Ex. 10 Perloyl IB 0.38 5.23.9 3.63 6.94 59.0/41.0 Ex. 11 Ammonium 0.1568 6.6 5.0 6.50 17.158.8/41.2 persulfate

EXAMPLE 12

[0191] A 3 l stainless steel autoclave was charged with 1,500 ml of ionexchanged water, 16.7 g of ammonium persulfate. After sufficientlyreplacing with nitrogen, the autoclave was charged with 822 g ofhexafluoropropylene (HFP) and then 103 g of ethylene in a vacuum state.The autoclave was cooled and left until the temperature was 15° C. andthe pressure became constant (2.2 MPaG) while stirring thepolymerization system with an electromagnetic stirrer. The autoclave wasthen charged with a 10% aqueous solution of sodium sulfite so that theratio became 6 g/hr by a plunger pump to start the reaction. Thepressure decreases as the reaction progresses and this decrease inpressure was compensated by adding ethylene. The polymerization reactionwas conducted at a constant temperature and pressure (15° C., 2.2 MPaG)for 29.5 hours.

[0192] After the reaction was finished, the remaining monomers werereleased into the air and the obtained emulsified dispersion body wascoagulated with hydrochloric acid, then washed with ion exchanged waterand dried at 120° C. until a constant weight was reached to obtain 150 gof the elastomeric polymer product. The average polymerization rate was2.7 g/hr/liter-water.

[0193] The composition of copolymer, number average molecular weight andweight average molecular weight of the product obtained by thepolymerization were measured by the analyzing method of ¹H-NMR and GPC.The product was a copolymer of 63.2% by mole of ethylene and 36.8% bymole of HFP, the number average molecular weight was 2.20×10⁵ (on apolystyrene basis), and the weight average molecular weight was9.49×10⁵.

EXAMPLE 13

[0194] A 6 l stainless steel autoclave was charged with 3 l of ionexchanged water, 150 g of ammonium perfluorooctanate, 2.4 g of sodiumhydroxide, 24 g of hydrogen phosphate disodium salt 12 hydrate, 110.4 gof t-butyl alcohol and 7.8 g of Perbutyl PV (containing 70% by weight oft-butyl peroxypivalate, available from NOF Corporation). Aftersufficiently replacing with nitrogen, the autoclave was charged with1,640 g of hexafluoropropylene (HFP) and then 201 g of ethylene in avacuum state. The autoclave was cooled and left until the Temperaturebecame 15° C. and the pressure became constant (2.1 MPaG) while stirringthe polymerization system with an electromagnetic stirrer. When thetemperature and pressure became constant, the autoclave was charged withan aqueous solution containing 0.186 g of iron (II) sulfate 7 hydrate,0.249 g of disodium ethylene diamine tetraacetate 2 hydrate and 6.0 g ofsodium hydroxymethane sulfinate 2 hydrate by a plunger pump to start thereaction. The pressure decreases as the reaction progresses and thisdecrease in pressure was compensated by adding ethylene. The reactionwas conducted at a constant temperature and pressure (15° C., 2.1 MPaG)for 10 hours.

[0195] After the reaction was finished, the remaining monomers werereleased into the air and the obtained emulsified dispersion body wascoagulated with hydrochloric acid, then washed with ion exchanged waterand dried at 120° C. until a constant weight was reached to obtain 723 gof the elastomeric polymer product. The average polymerization rate was25.3 g/hr/liter-water.

[0196] The composition of copolymer, number average molecular weight andweight average molecular weight of the product obtained by thepolymerization were measured by the analyzing method of ¹H-NMR and GPC.The product was a copolymer of 62.3% by mole of ethylene and 37.7% bymole of HFP, the number average molecular weight was 6.2×10⁴ (on apolystyrene basis), and the weight average molecular weight was2.74×10⁵.

[0197] Furthermore, the Mooney viscosity (ML 1+10, 100° C.) measured bythe following method was 66.

[0198] (Mooney viscosity (1+10, 100° C.))

[0199] The Mooney viscosity was measured according to ASTM-D1646 and JISK6300.

[0200] Measurement instrument: Automatic Mooney viscosity meter made byUeshima Seisakusho Co., Ltd.

[0201] Rotation number of rotor: 2 rpm

[0202] Measurement temperature: 100° C.

EXAMPLES 14 TO 16

[0203] E-HFP copolymer was obtained by emulsion polymerizing ethyleneand HFP in the same manner as in Example 13 except that the amount ofiron (II) sulfate 7 hydrate and disodium ethylene diamine tetraacetate 2hydrate and the reaction time were as indicated in Table 2.

[0204] The amount of the copolymer obtained, the average polymerizationrate, the composition of the copolymer, the number average molecularweight, the weight average molecular weight and the Mooney viscosity (ML1+10, 100° C.) in these Examples are indicated in Table 2. TABLE 2 Ex.13 Ex. 14 Ex. 15 Ex. 16 Amount of iron sulfate 0.186 0.093 0.048 0.005(g) EDTA-2Na2H₂O (g) 0.249 0.124 0.064 0.006 Polymerization time (hr) 1017 20 74 Average polymerization 25.3 14.4 11.9 2.5 rate(g/hr/liter-water) Amount of copolymer 723 730 749 576 obtained (g)Molecular weight (× 10⁴) Number average 6.2 9.91 12.05 21.64 Weightaverage 27.4 37.8 63.1 77.44 Mooney viscosity 64 75 98 148 (1 + 10, 100°C.) Composition of 62.3/37.7 62.6/37.4 63.2/36.8 62.5/37.5 copolymer(E/HFP: % by mole)

EXAMPLE 17

[0205] A 100 ml stainless steel autoclave was charged with 45 ml of ionexchanged water, 42.5 g of ammonium perfluorooctanate, 0.04 g of sodiumhydroxide, 0.4 g of disodium hydrogen phosphate 12 hydrate, 1.84 g oft-butyl alcohol and 0.13 g of Perbutyl PV (containing 70% by weight oft-butyl peroxy pivalate, available from NOF Corporation). Aftersufficiently replacing with nitrogen, the autoclave was charged with16.7 g of hexafluoropropylene (HFP) and then 2.02 g of ethylene in avacuum state. The autoclave was placed into a constant temperature waterbath shaker of 5° C. and was shaken until the pressure became constant(1.6 MPaG). When the pressure became constant, the autoclave was chargedwith an aqueous solution containing 0.0031 g of iron (II) sulfate 7hydrate, 0.0041 g of disodium ethylene diamine tetraacetate 2 hydrateand 0.1 g of sodium hydroxymethane sulfinate 2 hydrate by a plunger pumpto start the reaction. The reaction was conducted at 5° C. for 1 hour.

[0206] After the reaction was finished, the remaining monomers werereleased into the air and the obtained emulsified dispersion body wascoagulated with hydrochloric acid, then washed with ion exchanged waterand dried at 120° C. until a constant weight was reached to obtain 0.8 gof the elastomeric polymer product. The average polymerization rate was15.2 g/hr/liter-water.

[0207] The composition of copolymer, number average molecular weight andweight average molecular weight of the product obtained by thepolymerization were measured by the analyzing method of ¹H-NMR and GPC.The product was a copolymer of 60.1% by mole of ethylene and 39.9% bymole of HFP, the number average molecular weight (on a polystyrenebasis) was 4.36×10⁴, and the weight average molecular weight was8.83×10⁴.

EXAMPLE 18

[0208] 3.7 g of E-HFP copolymer was obtained by emulsion polymerizingethylene and HFP in the same manner as in Example 17 except that thepolymerization temperature was set to 25° C. The average polymerizationrate was 73.8 g/hr/liter-water.

[0209] The composition of copolymer, number average molecular weight andweight average molecular weight of the product obtained by thepolymerization were measured by the analyzing method of ¹H-NMR and GPC.The product was a copolymer of 58.6% by mole of ethylene and 41.4% bymole of HFP, the number average molecular weight (on a polystyrenebasis) was 4.10×10⁴, and the weight average molecular weight was8.12×10⁴.

EXAMPLE 19

[0210] A 3 l stainless steel autoclave was charged with 1.5 l of ionexchanged water, 75 g of ammonium perfluorooctanate, 1.2 g of sodiumhydroxide, 11.8 g of disodium hydrogen phosphate 12 hydrate, 55.2 g oft-butyl alcohol and 3.68 g of Perbutyl PV (containing 70% by weight oft-butyl peroxypivalate, available from NOF Corporation). Aftersufficiently replacing with nitrogen, the autoclave was charged with 826g of hexafluoropropylene (HFP) in a vacuum state and the temperature wasset to 15° C. Then 26 g of an ethylene/TFE monomer mixture (87.7/12.3%by mole) mixed in advance was press fitted until the pressure within theautoclave reached 0.85 MPaG. The autoclave was left until thetemperature was 15° C. and the pressure became constant (0.85 MPaG)while stirring the polymerization system with an electromagneticstirrer. When the temperature and the pressure became constant, anaqueous solution obtained by dissolving 0.018 g of iron (II) sulfate 7hydrate, 0.021 g of disodium ethylene diamine tetraacetate 2 hydrate and2.9 g of sodium hydroxymethane sulfinate 2 hydrate into 50 g of ionexchanged water was subjected to bubbling by nitrogen gas and theautoclave was then charged with this solution by a plunger pump to startthe reaction.

[0211] The pressure decreases as the reaction progresses and thisdecrease in pressure was compensated by adding ethylene/TFE monomermixture (91.7/8.3% by mole). The reaction was conducted at a constanttemperature and pressure (15° C., 0.85 MPaG) for 31.25 hours.

[0212] After the reaction was finished, the remaining monomers werereleased into the air and the obtained emulsified dispersion body wascoagulated with hydrochloric acid, then washed with ion exchanged waterand dried at 120° C. until a constant weight was reached to obtain 330 gof the elastomeric polymer product. The average polymerization rate was7 g/hr/liter-water.

[0213] The composition of this E-HFP-TFE copolymer was measured by theanalyzing method of ¹H-NMR and ¹⁹F-NMR, and the number average molecularweight and weight average molecular weight of this E-HFP-TFE copolymerwere measured by the analyzing method of GPC. The product was acopolymer of 54.0% by mole of ethylene, 40.4% by mole of HFP and 5.6% bymole of TFE, the number average molecular weight (on a polystyrenebasis) was 44000, and the weight average molecular weight was 62000.

COMPARATIVE EXAMPLE 1

[0214] A 2 l stainless steel autoclave was charged with 887 ml of ionexchanged water, 444 g of ammonium perfluorooctanate. After sufficientlyreplacing with nitrogen, the autoclave was charged with 544 g ofhexafluoropropylene (HFP) and then 70 g of ethylene in a vacuum state.The autoclave was heated by a circulating constant temperature bath andwas left until the temperature reached 65° C. and the pressure becameconstant (6.0 MPaG) while stirring the polymerization system with anelectromagnetic stirrer. The autoclave was then charged with 0.27 g ofammonium persulfate by a plunger pump to start the reaction. Thepressure decreases as the reaction progresses and this decrease inpressure was compensated by adding ethylene. The polymerization reactionwas conducted at a constant temperature and pressure (65° C., 6.0 MPaG)for 25 hours.

[0215] After the reaction was finished, the remaining monomers werereleased into the air and the obtained emulsified dispersion body wascoagulated with hydrochloric acid, then washed with ion exchanged waterand dried at 120° C. until a constant weight was reached to obtain 294 gof the elastomeric polymer product. The average polymerization rate was15.4 g/hr/liter-water.

[0216] The composition of copolymer, number average molecular weight andweight average molecular weight of the product obtained by thepolymerization were measured by the analyzing method of ¹H-NMR and GPC.The product was a copolymer of 64.0% by mole of ethylene and 36.0% bymole of HFP, the number average molecular weight (on a polystyrenebasis) was 1.08×10⁵, and the weight average molecular weight was9.12×10⁵.

EXAMPLES 20 TO 24 AND COMPARATIVE EXAMPLE 2

[0217] The elastomeric E-HFP copolymer prepared respectively in Examples12 to 16 and Comparative Example 1 was used. To 100 parts by weight(hereinafter “parts”) of the copolymer were added 30 parts by weight ofcarbon black (MT-C), 3.7 parts of peroxide type vulcanizing agent(Perbutyl Z), 2.5 parts of auxiliary vulcanizing agent(triallylisocyanate, available from Nippon Kasei Chemical Co., Ltd.) and3 parts of acid acceptor (MgO). Kneading was then conducted at roomtemperature using an open roll. All of the compounds had good adhesionto the roll and kneading was easy. The obtained rubber compound was putin a die, primarily vulcanized by press vulcanization and thensecondarily vulcanized by oven vulcanization to prepare the vulcanizate.The vulcanization properties at 160° C. were measured. The results areshown in Table 3.

[0218] The properties under normal conditions and heat resistance of theobtained vulcanizate were measured by the following method. The resultsare shown in Table 3.

[0219] (Vulcanization Properties)

[0220] During primary press vulcanization, the vulcanization curve at160° C. was obtained using a JSR-model Curastometer II. From this curve,the minimum viscosity (ML), vulcanization degree (MH), induction period(T₁₀) and optimum vulcanization time (T₉₀) were obtained.

[0221] (Properties Under Normal Conditions)

[0222] 100% modulus (M100), tensile strength at break (TB) and tensileelongation at break (EB) were measured according to JIS K6251 (1993) andhardness (Hs) was measured by the durometer type A described in JISK6253 (1997).

[0223] (Heat Resistance)

[0224] The rate of change in tensile strength at break (ΔTB), the rateof change in tensile elongation at break (ΔEB) and the rate of change inhardness (ΔHs) after 230° C.×72 hours of exposure in the air wasmeasured.

EXAMPLE 25

[0225] The elastomeric E-HFP-TFE copolymer prepared in Example 19 wasused. To 100 parts by weight (hereinafter “parts”) of the copolymer wereadded 30 parts by weight of carbon black (MT-C), 3.7 parts of peroxidetype vulcanizing agent (Perbutyl Z) and 2.5 parts of auxiliaryvulcanizing agent (triallylisocyanate, available from Nippon KaseiChemical Co., Ltd.). Kneading was then conducted at room temperatureusing an open roll. The compound had good adhesion to the roll andkneading was easy. The obtained rubber compound was put in a die,primarily vulcanized by press vulcanization and then secondarilyvulcanized by oven vulcanization to prepare the vulcanizate. Thevulcanization properties at 160° C. were measured. The results are shownin Table 3.

[0226] The properties under normal conditions and heat resistance of theobtained vulcanizate composition were measured. The results are shown inTable 3. TABLE 3 Ex. 20 Ex. 21 Ex. 22 Ex. 23 Ex. 24 Ex. 25 Com. Ex. 2Copolymer used Ex. 12 Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 19 Com. Ex. 1Mooney viscosity (1 + 10, 100° C.) 206 66 75 98 148 138 77 Vulcanization(160° C.) ML 0.9 0.2 0.4 0.4 0.5 0.3 0.35 MH 4.95 3 3.5 3.75 4.75 2.73.4 T₁₀ 0.3 0.3 0.4 0.3 0.2 0.4 0.3 T₉₀ 2.5 2.5 4 3.1 3.7 3.5 2.5Properties under normal condition M100 84 59 60 67 75 48 80 TB 254 186216 230 255 183 154 EB 220 200 230 220 220 260 170 Hs 70 70 70 71 71 7169 Heat resistance (230° C. × 72 hr) ΔTB (%) −42.5 −44.9 −40.2 −45.9−43.8 −25 −51.6 ΔEB (%) −15.7 −12.7 −11.6 −12.7 −8.7 40.1 −37.3 ΔHs (%)1 −2 −1 −1 −2 0 2

1. A process for preparing an elastomeric ethylene-hexafluoropropylenecopolymer, which comprises emulsion-polymerizing ethylene,hexafluoropropylene, and when in demand, a monomer copolymerizabletherewith in an aqueous medium at −20° C. to 40° C. using a redox typeinitiator.
 2. The process of claim 1, wherein said copolymerizablemonomer is a fluorine-containing olefin.
 3. The process of claim 2,wherein said fluorine-containing olefin is selected from the groupconsisting of tetrafluoroethylene, vinylidene fluoride,chlorotrifluoroethylene, trifluoroethylene, pentafluoropropylene andperfluoro(alkyl vinyl ether), or at least two members of the monomers.4. The process of claim 1, wherein copolymerization is conducted in thepresence of a redox type initiator by using a radical polymerizationinitiator and a reducing agent comprising metal ion, hydroxymethanesulfinate and ethylenediaminetetraacetic acid or a salt thereof.
 5. Theprocess of claim 4, wherein said metal ion is an iron ion.
 6. Theprocess of claim 4, wherein said radical polymerization initiator is anorganic peroxide or persulfate.
 7. The process of claim 6, wherein saidorganic peroxide is a peroxyester.
 8. The process of claim 7, whereinsaid organic peroxide is t-butyl peroxypivalate.
 9. The process of claim1, wherein emulsion polymerization is conducted under a polymerizationpressure of 0.49 to 10 MPaG.